Apparatus for grooving pavement

ABSTRACT

Apparatus for forming a series of spaced parallel grooves in the surface of a newly laid pavement slab characterized by engaging the surface of the pavement slab with a molding cylinder having a plurality of circumferential ribs formed thereon and moving the molding cylinder across the surface of the pavement slab while simultaneously rotating the molding cylinder about its longitudinal axis at a rate slightly greater than a free roll. Means are disclosed for preventing damage to the parallel edges of the pavement slab during the grooving process, and means are disclosed for simultaneously spraying water on the surface of the pavement slab and the surface of the molding cylinder during the grooving process.

United States Patent 1191 Grist et a1.

[ APPARATUS FOR GROOVING PAVEMENT [75] Inventors: Warren W. Grist, Yukon; Adolph R.

Petersik. Oklahoma City. both of Okla.

I73] Assignee: CMl Corporation. Oklahoma City.

Okla.

[22] Filed: July 27. 1972 [2]] App]. No.: 275.460

1 1 Apr. 1, 1975 Barton 404/93 Perkins v. 404/75 [57] ABSTRACT Apparatus for forming a series of spaced parallel grooves in the surface of a newly laid pavement slab characterized by engaging the surface of the pavement slab with a molding cylinder having a plurality of eircumferential ribs formed thereon and moving the molding cylinder across the surface of the pavement slab while simultaneously rotating the molding cylinder about its longitudinal axis at a rate slightly greater than a free roll. Means are disclosed for preventing damage to the parallel edges of the pavement slab during the grooving process. and means are disclosed for simultaneously spraying water on the surface of the pavement slab and the surface of the molding cylinder during the grooving process.

5 Claims, 9 Drawing Figures BALKUROI'ND ()I" THIZ IXYIYNI'ION l. Field of the Invention The invention relates generally to method and apparatus for treating the surface of concrete. and more specifically. but not by \vay of limitation. to method and apparatus automatically forming parallel grooves in the urface of a nevvly laid pavement slab 2, Brief Description of the Prior Art It has become desirable in the construction of pavement slabs for highvvays and airport runvvays to provide grooves in the surface of the slab to provide runoff channels for vvater to prevent the tires of automobiles or aircraft from riding on the surface of the water on the pav ement slab thereby causing los ofcontrol of the vehicle. This phenomenon is knovvn an aquaplaning.

Knovvn examples of the prior art teach various systems for providing grooves in the surface of pavement slabs. One method of forming such grooves is to use a rotary savv blade to cut grooves in the surface of a cured pavement slab. This method is extremely slovv and evpensive. Another I\'IIO\\'I'I method of achieving this objective is to dravv a sledge. having spaced parallel ribs formed on the bottom side thereof. across the surface of a nevvly laid pavement slab to forln grooves therein. Apparatus for practicing thi method has prov ed somevvhat unsatisfactory due to damage done thereby to the surface of the pavement slab. The prior art also teaches the use of cylinders having circumferential ribs formed therein which are rolled freely across the surface of a nevvly laid pavement slab to form grooves therein. This method has also proved unsatisfactory since it tends to force a portion of the newly laid pavement along in front of the molding cylinder vvhich also damages the surface of the nevvly laid pavement slab. Yet another knovvn prior art system utilizes the counter rotation of the molding cylinder as the molding cylinder is traversed across the surface of the nevvly laid pavement slab. This latter method. as vvell as the previously mentioned methods, provides less than satisfactory surface finish to the newly laid pavement slab,

for

SUMMARY OF THE INVENTION The present invention contemplates a method of forming a series of spaced parallel grooves in the surface of a newly laid pavement slab having substantial parallel edge portions comprising the steps of engaging the surface of the pavement slab with the molding cylinder having a plurality of spaced circumferential ribs formed on the cylindrical surface thereof. pressing the molding cylinder into the surface of the pavement slab to imhed a portion of the ribs in the pavement and to press a portion of the cylindrical surface of the molding cylinder against the surface of the pavement. moving the molding cylinder over the surface of the pavement slab in a direction substantially normal to the longitudinal axis thereof and rotating the molding cylinder about the longitudinal axis thereof in the direction of movement over the surface of the pavement at a rotational rate greater than the rotational rate of the molding cylinder if rolled freely over the surface of the pavement.

An object of the present invention is to provide an improved method of forming a series ofspaced parallel grooves in the surface of a nevvly laid pavement slab (ill \vhich \vill provide a substantially smooth surface \vith parallel grooves formed therein.

Another object of the present invention is to provide an improved method of forming a serie of paced parallel grooves in the surface of a nevvly laid pavement slab vv hich vv ill not damage the surface of the pavement slab.

Yet another object of the present invention is to pro vide an improved method and apparatus for forming a series of spaced parallel groove in the surface of a nevv Iy laid pavement slab vv hich vv ill neither damage the surface of the pavement slab nor damage the parallel edges of the pavement slab.

Another object of the present invention is to provide an improved apparatus for forming a eries of spaeed parallel grooves in the surface of a nevvly laid pavement slab vvhich is of simple construction. is reliable in oper ation. and is economical to maintain.

Other objects and advantage of the present invention will be evident from the follovving detailed description vvlien read in conjunction vvith the accompanying dravvings.

IiRIl-IF DESCRIPTION ()I THE DRAWINGS FI(i. l is a plan v ievv of the apparatus of the present invention.

FIG. 2 is aside elevation v ievv of the apparatus of the present invention taken along line 2-2 of Fl(i. I.

FIG. 3 is a front elevation vievv of the apparatus of the present invention taken along line 3 3 of FIG. 2.

FIG. 4 is a cross-sectional vievv taken along line 4-4 of Fl(i. 1.

FIG. 5 is a partial plan vievv talven substantially along line 5-5 of FIG. 4 to more clearly illustrate the rail assembly of the present invention.

FIG. 6 is an enlarged partial cross 'ectional taken along line fifi of FIG. 4 to more clearly trate the carriage and grooving assemblies of the em invention.

FIG. 7 is an enlarged partial cross-sectional taken along line 7-7 of FIG. 6 to more clearly trate the carriage and grooving assemblies of the ent invention.

FIG. 8 is an enlarged partial cross-sectional view taken along line 88 of FIGv 5 to more clearly illustrate construction details of the rail assembly of the present invention.

FIG. 9 is an enlarged partial cross-sectional vievv illustrating a typical configuration of the surface of the molding cylinder of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the dravvings. and to FIGS. 1-4 in partic' ular. the apparatus of the present invention is generally designated by the reference character [0. The appara tus HI generally comprises a frame assembly I2. a rail assembly 14 suspended beneath the frame assembly l2. a carriage assembly 16 carried by the rail assembly 14 and adapted for vertical movement thereon. and a grooving assembly 18 suspended beneath the carriage assembly 16.

The frame assembly 12 is provided vvith a support assembly 20 at each of the four corners thereof to stipport the frame assembly 12 in a generally IIOII'IUIIILII position on the ground. Each support assembly 20 includes a support vvheel 22 journaled thereon. Each stipvievv illuspresvievv illuspresport a sembly further includes a pair of mutually telescoping elements 24 and 26 which provide mean for adjusting the height of the frame assembly I2 relati\e to the ground.

power unit 28 is mounted on the frame assembly l2 and is dri\ ingly connected to each support wheel 22 to pro\ ide for aid or rearward mo\ enieiit of the appa ratu I0 o\ er the groundv The power unit 28 may be of any suitable type but preferably includes a diesel type internal combustion engine as the prime nio\ er The power unit 28 preferably includes a comentional hydraulic pump dri\en by the prime mo\er which is in turn connected by means of hydraulic lines (not sltt \\ttl to a hydraulic motor 30 carried by each support as embly 20 and dri\ ingly connected to each support wheel 22. control console 32 is mounted on the frame a sembly I2 and pro ides means for manual op erational control of the apparatus l0 by an apparatus operator.

.\t each upport assembly 20. the telescoping element 26. upon which a support \\ltcel 22 is journaled. is free to rotate within the respective telescoping element 24 about a substantially vertical ayis. This arrangement permits each support wheel 22 to be re- \ol\ed about this same \ertieal avis thereby providing means of steering control for the frame l2. liach tclescoping element 26 is pro\ided with an elongated arm 34 which i fiyedly ecured at one end thereof to the respecti\e telescoping element 26. The opposite end of each elongated arm 34 is pivotally secured to a hydrau lieally actuated steering linkage 36 of conventional design which need not be described in detail herein. first sensor assembly 38 and a second sensor assembly 40 are mounted on the frame assembly l2. The sensor assemblies 38 and 40 are adapted to engage a st ringline 42 to pro\ ide automatic steering control of the apparatus I0. This method of position feedback control of the apparatus I0 is well known and is contained in IQSi Pat. No. 3.423.515). to (I. W. Swisher .Ir.. et all and will. therefore. not be described in detail herein.

The rail assembly I4 is suspended beneath the frame assembly I2 by means of a pair of telescoping struts 44. The upper portion 46 of each telescoping strut 44 is fixedly secured to the frame assembly l2. while the lower portion 48 of each telescoping strut 44 is pivotally secured to the rail assembly I4. Each telescoping strut 44 is equiped with a two-way hydraulic cylinder 45 disposed within interconnecting the upper portion 46 and the low er portion 48 thereof to alternately raise and lower the rail assembly I4 relative to the frame assembly I2.

As shown in FIG. 5. the rail assembly I4 comprises a pair of elongated parallel rails 50 and 52 rigidly secured together by a plurality of cross members 54. At one end 56 of the rail assembly I4 a cross member 58 rigidly interconnects the elongated rails 50 and 52. while at the opposite end 60 of the rail assembly 14a cross member 62 rigidly interconnects the elongated rails 50 and 52. The elongated rails 50 and 52 are preferably formed of channel steel ha ing a (shaped cross section. It will be noted that the tlanges of the elongated rails 50 and 52. respectively. extend horivontally away from one another.

The elongated rail 50 comprises four segments 64. My (1H. and 70. while the elongated rail 52 comprises four rail segment 72. 74. 76. and 78. The ends of abutting rail segments are typically secured together by (ill means ola pivotal pin connection beneath the lower flanges thereof. The upper tlange of abutting rail segments are adjustably secured together by means of a turnbuckle as embly 82 secured at the opposite ends thereof to respecti\c brackets 84 formed on the upper flanges of the adjacent rail segments. This particular arrangement provides the capability of adjusting the alignment of the rail segments of the respective elongated rails 50 and 52. This arrangement also provides the capability of substituting rail segments of various lengths to proyide \irtually any desired length of the rail assembly l4. It should be noted that. while a simple mechanical turnbuckle assembly 82 is disclosed herein for the purpose of adjusting the alignment of the rail assembly I4. it may be desirable. in certain applications. to substitute a two-way hydraulic cylinder for one or more turnbuckle assemblies to provide automatic adjustment of the rail assembly l4.

The pre\iously mentioned lower portion 48 of each telescoping strut 44 is pivotally secured to a respectue cross member 86 rigidly interconnecting the elongated rails 50 and 52. See FIG. 8. A bracket 88 extends up' w ardly from each elongated rail 50 and 52 adjacent the point of intersection with the cross member 86. A tenion coil spring )0 interconnects each bracket 88 and the respective lower portion 48 of a telescoping strut 44. The coil springs )0 are of substantially the same spring rate and pro\ide means for biasing the rail assembly I4 into a plane substantially parallel to the suh stantially ltnt'iYUttltll frame assembly 12.

A drive shaft )2 is journaled at the opposite ends thereof in one end 56 ofthe rail assembly I4. A pair of sheaves )4 are keyed to the drive shaft )2 and are adapted to frictionally engage a steel cable wrapped therearound. A driv e motor 96. preferably a two-way hydraulic motor. is mounted on the end 56 of the rail assembly I4 and is suitably connected to the drive shaft )2. such as by a sprocket and chain drive. to provide rotational movement thereof The drive motor 96 is suitably connected to the power unit 28, preferably by means of hydraulic lines. to receive power for rotating the drive shaft )2.

A pair of sheaves 98 are each journalcd on a respec' the bracket I00 which is fixedly secured to the cross member 62 at the opposite end 60 of the rail assembly 14. The function of the dri e motor )6. drive shaft 92. and sheaves 94 and )8 described above will be explained in greater detail hereinafter.

The carriage assembly I6 comprises a pair of parallel roller supporting members I02 and I04 which are rigidly secured to a pair of elongated parallel members I06 and 108 thereby forming a rigid rectangular frame. A pair of rollers IIO are hori7ontally journaled on the roller supporting member I02 and rollingly engage the inner surface of the lower flange of the elongated rail 50. A pair of rollers lI2 are vertically journaled on the roller supporting member I02 arid rollingly engage the web of the elongated rail 50. A pair of rollers II4 are horiyontally journaled oit the roller supporting member I04 and rollingly engage the inner surface of the lower flange of the elongated rail 52. A pair of rollers II6 are vertically journaled on the roller supporting member I04 and rollingly engage the web of the elongated rail 52. It will readily be apparent that the arrangement of the rollers I I0. I I2. I14. and I I6 permits the carriage assembly I6 to rollingly traverse the entire length ofthe frame assembly 12 by rolling along the elongated rails 50 and 52. .-\n end plate II8 rigidly interconnects the adjacent ends of the elongated parallel members I06 and I08. Another end plate I20. identical to end plate I I8. rigidly interconnects the opposite adjacent ends of the elongated parallel members I06 and I08. bracket I22 ha\ ing outvvardly and dovvnvvardly e\tending arms I24 and I26 formed on the opposite ends thereof is fixedly secttred to the end plate II8. A second bracket I28 having outvvardly and downwardly extending arms I30 and 132 formed on the opposite ends thereof is fixedly secured to the end plate I20. The function of the arms I24. I26. I30 and I32 will be explained in detail hereinafter.

A pair of sul'istantially identical steel cables I34 and I36 are fixedly secured at the first ends I38 and I3) thereof to the elongated parallel member I06 of the carriage assembly I6. See FIG. 5. The cables I34 and I36 extend beneath the frame assembly I2 to the respective sheaves )8. upward and around the respecti e sheaves )8 across the upper portion ofthe rail assembly l4 to the respeeti c sheaves )4 keyed on the drive shaft )2. The cables I34 and I36 extend around the respective sheaves )4 at least l times and extend therefrom beneath the rail assembly I4 to the elongated parallel member I08 \v here the opposite ends I40 and I4] of the cables I34 and I36. respccti\ely. are fixedly ccured to the elongated parallel member I08 of the carriage assembly I6. The wrapping ofthe steel cables I34 and I36 around the respective sheaves )4 provides frictional engagement therebetween thereby causing the rotational movement of the sheaves )4 in response to the drive motor )6 to impart linear moyement to the carriage assembly I6 along the rail assembly I4 via the cables I34 and I36. It will be readily apparent that rotation of the drive motor )6 in one direction vvill cause the carriage assembly l6 to roll along the rail assembly I4 in a corresponding linear direction while. alternately. rotation of the drive motor )6 in the opposite direction will cause the carriageassembly I6 to roll linearly along the rail assembly I4 in a corresponding opposite direction.

The grooving assembly I8 includes a support frame I42 and a molding cylinder I44journaled thereon. See FIGS. 5 and 6. The support frame I42 includes an elongated horizontal member I46 with a downwardly ex tending vertical member I48 fixedly secured to one end thereof. and with a second vertical member I50 fixedly secured to the opposite end thereof and extending both upwardly and downwardly from the hori/ontal member I46. Angle brackets I52 and I54 are fixedly secured to the upper surface of the horizontal member I46 and extend upwardly therefrom in spaced parallel relation Each bracket I52 and I54 includes a vertically aligned elongated slot I56 formed therein.

The support frame I42 is pivotally suspended beneath the carriage assembly I6 by means of bolts or pins I58 slidably extending through the slots I56 in the respective brackets I52 and I54 and fixedly secured in the respective end plates II8 and 120 of the carriage assembly 16. This means of attachment of the support frame I42 to the carriage assembly I6 permits the support frame I42 to pivot about a substantially horizontal axis relative to the cart'iage assembly I6, and to mine substantially vertically relative to the carriage assembly I6 by means of a sliding action of the slots I56 relative to the bolts I58.

A coil tension spring I60 interconnect the outer end portion of each arm I24. I26. I30 and I32 of the Ctll riage assembly I6 and the horizontal member I46 of the support frame I42. The springs I60 prov idc a constant spring bias to urge the upport frame I42 into a substantially \ertieal pendant position beneath the pivotal connection between the upport frame I42 and the carriage assembly I6.

A bracket I62 is fixedly secured to the upper end portion of the vertical member I50. dri\e motor I64 is fixedly secured to the bracket I62 and a hori/ontally disposed drive shaft I66 e\tends outvvardly therefrom through the brackets I62. chain dri\e procket I68 is keyed to the drive shaft I66. The drive motor I64 is preferably a reversible hydraulic motor which receives its power through hydraulic lines tnot shounl connccted to the povv er unit 28. Although the drive motor is preferably of the hydraulic typc other suitable drive motor may be substituted thclefor uch as an electric motor,

The molding cylinder I44 includes a first shaft stub I70 secured to the first end portion I72 thereof and coa\ial thereuitlr second shaft stub I74 is secured to the second end portion I76 of the molding cylinder I44 coaxial therewith. lhc first shaft stub I70 extends through the vertical member I50 and is iournaled therein in a stntable bearing I78. The second shaft tub I74 extends through the \crtical member I48 and is iournaled therein in a uitable bearing I80. chain dri\e sprocket I82 is keyed to the outer end portion of the lirst shaft stub I70. drive chain I84 driv ingly en gages the chain drive sprockets I68 and I82 thereby prroiding means for the rotation of the molding cy linder I44 in response to rotary power furnished by the drive motor I64.

A plurality ofcireumlcrential ribs I86 are formed on the cylindrical periphery I88 of the molding cylinder I44. The ribs I86 are preferably equally spaced along the periphery I88 of the molding cylinder I44 and are in parallel relation to one another,

In a preferred embodiment the molding cylinder I44 has a length of approximately 10 feet and a cylindrical diameter of approximately l0 inches, The cireumferen tial ribs 186 are preferably spaced approximately W4 inches apart along the cylindrical periphery I88 of the molding cylinder 144. The width of each circumferential rib I86 is preferably approximately .6 inch and the height of each circumferential rib I86 from the periphery I88 of the molding cylinder I44 is also approxi mately A inch. As shown in FIG. 9, the cross section of each circumferential rib I86 is substantially in the form of a triangle with a radius formed on the apex ofthe tri angle and with fillets formed between the outer legs of the triangle and the periphery I88 ofthe molding cylinder I44.

It should be noted that the molding cylinder I44 may suitably be formed in any number of configurations. and the detailed description of a single preferred construction of the molding cylinder I44 should not be construed to limit the present invention in any way. It will be readily apparent to those skilled in the art that various forms of spacing and shaping of the circunifer ential ribs I86 on the molding cylinder I44 may be rc quired to meet highway or runway design requirements set forth in various construction contracts.

It has been found that a suitable material for the construction of the molding cylinder I44 is aluminum pipe haung a nominal diameter of it! inches ()ther suitable materials may be used for the construction olthe mold ing cylinder I44 nicluding steel.

On each side of the frame l2 are mounted two \erti' cally oriented truts IJII as shown in l-IUS I. 2. 3 and 4. I ach strut I9" i |i\edly secured to the frame I2 by means of a pair of hori/ontal parallel members I92. I-ach strut I9" is in the form of a rectangular tube. A rectangular member I94 i recei ed in each strut I90 and e\tends downwardly therefrom. The members I94 are adapted to mow \ertically within the respective strut I90 in telescopic fashion. Each member I94 is locked in a predetermined position within the respecti\e strut I90 by means of a pair of hexagonahhcaded cap screws I96. or the like. which are threadcdly secured in the respectne strut I90 and bear against the member I94.

The lower end portion 198 of each member I94 is sired and shaped to receive a hori/ontally disposed rectangular member 200 which is aligned substantially parallel to the previously discussed members I92. Each member 200 is locked in a predetermined position within the lower end portion I98 by means of a pair of locking cap screws I96. or the like. threadedly secured in the lower end poi'tioii I98 and bearing on the rectangular member 200.

The inwardly extending free ends 202 of the respec the members 200 on each side of the frame assembly I2 are interconnected by a sul'istantially' llat plate 204. The plate 204 is preferably welded to the upper surface of the respective member 200 and extends inwardly from the free ends 202 thereof. The inner edge 206 of each plate 204 is aligned substantially with the longitudinal avis of the molding cylinder I44. liach plate 204 is preferably positioned on the respective members 200 such that it is inclined outwardly and slightly upwardly from a plane substantially parallel to the surface of the pavement slab from the inner edge 206 thereof as shown in FIG. 4. The length ofeach plate 204 along the edge 206 thereof is preferably at least one-half the length of the molding cylinder I44.

When properly positioned. the plates 204 extend in wardly over the respective adjacent outer edges of the concrete pavement slab to be grooved. The edge 206 of each plate 204 will be positioned slightly above the upper surface of the pavement slab.

Vertical adjustment of the rectangular members I94 within the respective struts I90 may be readily obtained by means of conventional screw jacks 208 installed in the respective upper end portions 210 of the struts I90. When proper vertical positioning is obtained by means of the screw jacks 208. the members I94 may be locked in proper position by tightening the respectne cap screws I96 in the respecti e struts I90.

'llic pre iously described plates 204 and the struc ture for supporting the plates 204 beneath the frame assembly I2 provide simple and el'fecti e means for prc\enting the molding cylinder I44 from breaking out. or otherwise damaging the edge portions of the pavement s'lab during the grooving operation. It will be readily apparent that when the molding cylinder I44 nears an edge portion of the pavement slab it will engage a respective adjacent plate 204 and will be sup ported thereby abo\ e the edge portion ofthe pavement slab.

Under certain circumstances it may be desirable to spray the surface of the concrete pavement slab and/or the peripheral urface INN of the molding cylinder I-I-I with water. lhis may be accomplished by the addition of a water sprinkling apparatus comprising a pair of hollow spi'iiiklei bars 2I2 which are rigidly secured to the outer end portions of the arms I24. I26. I30 and I32 of the carriage assembly I6 as shown in HUS. 6 and 7. lach sprinkler bar 2l2 includes a plurality of sprinkler heads 214 mounted along the length of the prinkler bar 2I2 in spaced relation. The sprinkler bars 212 are connected by means of water hoses tnot shown) to a water supply tank 216 carried by the frame assembly I2. The length of each sprinkler bar 212 is preferably substantially equal to the length ofthe molding cylinder I44. In the preferred embodiment this length is approvimately III feet. It should be noted that this sprinkler apparatus is also useful for washing the molding cylinder 144 after completion of a pa\ement grow ing operation to remove concrete materials or the like which may remain on the periphery thereof.

OPERATION ()l THE PREFERRED EMBODIMENT In operation, the apparatus III of the present in\ention is positioned over a concrete pavement slab as shown in FIGS. I. 2. 3 and 4. The longitudinal axis of the apparatus It! is positioned in substantial alignment with the longitudinal axis of the pavement slab. The plates 204 are then positioned by means of the previously described adjustments such that the inner edges 206 thereof extend inwardly over the respective edge portions of the pavement slab and are positioned slightly above the upper surface of the pavement slab. The rail assembly I4 is then lowered beneath the frame assembly I2 by means of the telescoping struts 44 until the grooving assembly I8 rests on one of the plates 204. The drive motor 96 is then activated to move the car riage assembly I6 across the apparatus It) on the rail assembly I4 in the direction of arrow 2I8 in FIG. 3, with the molding cylinder I44 pressing into the upper surface of the pavement slab as it moves off the sup porting flat plate 204.

As the drive motor 96 is actuated. the drive motor I64 is also actuated to rotate the molding cylinder I44 in the direction of arrow 220 in FIG. 3, about its longi tudinal axis in the support frame I42 of the grooving assembly I8. The rotational speed of the drive motor I64 and the direction of rotation of the drive motor I64 is adjusted such that the molding cylinder I44 is rotated in the direction of free roll across the surface of the pancment slab but at a rotational speed slightly greater than that of a free roll. The rotation of the molding cylinder at a speed slightly greater than that of a free roll has been found by experimentation to pro \ide optimum grooving of the surface of a concrete pavement slab.

When the carriage assembly I6 has traversed the full width of the apparatus It), the molding cylinder I44 engages the flat plate 204 on the side of the apparatus III opposite its starting point and the drive motors 96 and I64 are stopped, The apparatus III may then be moved forward a distance approximately equal to the length of the molding cylinder I44. The process, described above. may then be reversed with the molding cylinder I44 traversing the pavement slab in the opposite direction of arrow 222 iii FI(i. 4 but. as noted above. the

molding cylinder I44 will be rotated in the direction of arrow 224 in FIG. 4 by the drive motor I64 at a rota tional rate slightly greater than that ot a free roll. This process may he repeated any nuniher of times to provide trans\crsc grooving in the surface of a concrete pavement slah.

lf conditions warrant. water may he introduced into the sprinkler hars 212 from the water supply tank 2T6 during the traversing of the molding cylinder I44 and a desired amount of water will he spray ed on the pavement slah and the molding cylinder 144 through the sprinkler heads 214.

It should he noted that the coil tension springs I60 ill provide a constant downward pressure of the molding cylinder I44 on the surface of the concrete pa ement slah during the grooving operation. while permit ting the molding cylinder H4 to accommodate any slight irregularities in the surface of the concrete slah such as may he encountered in a crowned pavement slah.

Under certain circumstances it may also he desirahle to traverse the same grooves in the pavement slah more than once with the molding cylinder 1-14. It will he readily apparent that this may he accomplished hy simply reversing the dri\e motors 96 and 164 as noted ahove to reverse the direction of tra\ erse oy er the same grooves.

If it is desired to make all traverses across the pave ment slah in the same direction. this may he accomplished in the following manner. The rail assemhly H is first raised. after the initial traverse. a sufficient amount for the molding cylinder 144 to clear the surface of the pavement slah. The drive motor )6 is then reversed to move the carriage and grooving assemhlies l6 and I8 hack to the starting point. The apparatus 10 is then moved forward. if desired. to the next grooving position on the pavement slah, The rail assemhly I4 is then lowered to its proper grooving position and the grooving process is repeated as descrihed ahove.

It will he readily apparent that the invention is well suited to meet the previously stated ohjectives contained herein. Changes may he made in the construction and arrangement of parts or elements of the apparatus as disclosed herein without departing from the spirit and scope of the present invention.

\Vhat is claimed is:

I. An apparatus for forming a series of spaced parallel grooves in the surface of a newly laid pavement slah having suhstantially parallel opposite edge portions comprising:

a maching having opposite side portions. a front end portion and a rear end portion. and movahle lottgi tudinally over said pavement slah:

a molding cylinder having opposite end portions and disposed intermediate said machine and said pavement slah. said molding cylinder having a longitudinal rotational axis and having a plurality of spaced circumferential rihs formed on the cylindrical stirface thereof.

means for journally securing said molding cylinder to said machine with the longitudinal rotational axis thereof in substantial alignment with the direction of movement of said machine over said pavement slab;

means for raising said molding cylinder above said pavement slah:

means carried by said machine for pressing said Ill Ill

molding cylinder into the surface of said pa\emenl slah: means carried by said maching for min ing said mold ing cylinder in er the surface of said pav ement slah; means carried hy said machine for rotating said molding cylinder ahout the rotational a\is thereof in the direction of movement o\cr the surfate of said pavement slah at a rotational rate greater than the rotational rate ofsaid molding cy linder if rolled freely over the surface of said pavement slah; and. means carried on each side portion of said machine for preventing the circumferential rihs of said molding cylinder from intersecting the respectoe edge portions of said pa\ement slah. said means comprising a flat plate secured to each side portion of said machine. each plate having an inwardly e\- tending edge portion positioned ahove aml lightly inwardly ofthe respecthe adjacent edge portion of said pavement slah. and each plate lying in a plane suhslantially parallel to the surface of said pavement slah.

2. The apparatus as defined in claim I wherein said means for journally securing said molding cylinder to said machine comprises:

a suhframe ha\ing opposite end portions. said mold ing cylinder heing iournaled at the opposite end portions thereof in the respective opposite end portions of said suhframci connecting means interconnecting said suhframe and said machine for supporting said suhframe heneath said machine in a mannerpermitting movement of said suhframe alternately from a position adjacent to one side portion of said machine to a position adjacent to the opposite side portion of said machine; and

wherein said means carried by said machine for rotating said molding cylinder ahout the rotational axis thereof is characteri/ed further to lltCltlLlLl a dri\e motor mounted on said suhframe and dri\ ingly connected to said molding cylinder for rotation thereof.

3. The apparatus as defined in claim 2 wherein said drive motor is reversihle for rotation of said molding cylinder in either direction relative to said suhframe.

4. The apparatus as defined in claim 2 herein said suhframe is charactcriled further to includel a carriage assemhly connected to said connecting means:

a support frame. having opposite end portions. pi\ otally secured to said carriage assembly and depending therefrom. said molding cylinder heing journaled at the opposite end portions thereof in the opposite end portions of said support frame;

spring means interconnecting said carriage assemhly and said support frame for urging said support frame into a substantially pendant position heneath said carriage assemhly about the axis of pivotal se curement therehetweent S. The apparatus as defined in claim 4 wherein the axis of pivotal securement between said carriage as semhly and said support frame is substantially parallel to the longitudinal rotational axis of said molding cylindcr. 

1. An apparatus for forming a series of spaced parallel grooves in the surface of a newly laid pavement slab having substantially parallel opposite edge portions comprising: a maching having opposite side portions, a front end portion and a rear end portion, and movable longitudinally over said pavement slab; a molding cylinder having opposite end portions and disposed intermediate said machine and said pavement slab, said molding cylinder having a longitudinal rotational axis and having a plurality of spaced circumferential ribs formed on the cylindrical surface thereof; means for journally securing said molding cylinder to said machine with the longitudinal rotational axis thereof in substantial alignment with the direction of movement of said machine over said pavement slab; means for raising said molding cylinder above said pavement slab; means carried by said machine for pressing said molding cylinder into the surface of said pavement slab; means carried by said maching for moving said molding cylinder over the surface of said pavement slab; means carried by said machine for rotating said molding cylinder about the rotational axis thereof in the direction of movement over the surface of said pavement slab at a rotational rate greater than the rotational rate of said molding cylinder if rolled freely oVer the surface of said pavement slab; and, means carried on each side portion of said machine for preventing the circumferential ribs of said molding cylinder from intersecting the respective edge portions of said pavement slab, said means comprising a flat plate secured to each side portion of said machine, each plate having an inwardly extending edge portion positioned above and slightly inwardly of the respective adjacent edge portion of said pavement slab, and each plate lying in a plane substantially parallel to the surface of said pavement slab.
 2. The apparatus as defined in claim 1 wherein said means for journally securing said molding cylinder to said machine comprises: a subframe having opposite end portions, said molding cylinder being journaled at the opposite end portions thereof in the respective opposite end portions of said subframe; connecting means interconnecting said subframe and said machine for supporting said subframe beneath said machine in a manner permitting movement of said subframe alternately from a position adjacent to one side portion of said machine to a position adjacent to the opposite side portion of said machine; and wherein said means carried by said machine for rotating said molding cylinder about the rotational axis thereof is characterized further to include: a drive motor mounted on said subframe and drivingly connected to said molding cylinder for rotation thereof.
 3. The apparatus as defined in claim 2 wherein said drive motor is reversible for rotation of said molding cylinder in either direction relative to said subframe.
 4. The apparatus as defined in claim 2 wherein said subframe is characterized further to include: a carriage assembly connected to said connecting means; a support frame, having opposite end portions, pivotally secured to said carriage assembly and depending therefrom, said molding cylinder being journaled at the opposite end portions thereof in the opposite end portions of said support frame; spring means interconnecting said carriage assembly and said support frame for urging said support frame into a substantially pendant position beneath said carriage assembly about the axis of pivotal securement therebetween.
 5. The apparatus as defined in claim 4 wherein the axis of pivotal securement between said carriage assembly and said support frame is substantially parallel to the longitudinal rotational axis of said molding cylinder. 